Golden lancehead description

Unique to a single, tiny island off the coast of the Brazil (1), the golden lancehead (Bothropoides insularis) is a highly venomous pitviper, a group of vipers distinguished by the conspicuous heat-sensitive pits (‘loreal pits’) between the nostril and eye. As in other vipers, the head is distinct from the body, the tail is relatively short, and the scales are rough (3). As its common name suggests, the body of the golden lancehead is yellowish in colour, sometimes with faint markings, and with a dark tip to the tail (4). The head is shaped like a lance (5), and the eyes have elliptical pupils (3). The female golden lancehead grows considerably larger than the male (2).

The golden lancehead is thought to be most closely related to the jararaca (Bothropoides jararaca)(2)(6), from which it may have diverged when its island home became separated from the mainland around 11,000 years ago (4)(7). The two species can easily be distinguished by differences in colouration and patterning, and the golden lancehead is also smaller, with a relatively longer tail, a longer head, and shorter fangs (2)(4).

Related species

Golden lancehead biology

The golden lancehead has developed a number of physiological and behavioural differences to the Bothropoides species of the mainland. Like other pitvipers, it uses its heat-sensitive pits to detect prey, and possesses a pair of long, hollow fangs that fold against the roof of the mouth when not in use, being brought forward to inject venom (3).

However, unlike the mainland species, which feed mainly on rodents, the golden lancehead has switched to a diet of birds due to an absence of small mammals on Queimada Grande . Whereas rodents are bitten and then released, the snake then tracking the prey until it has safely been overcome by the venom, the golden lancehead must retain hold of the bird and kill it quickly, to prevent it flying away and being impossible to follow. The bird is therefore held in the mouth after being bitten, and the venom of the golden lancehead works unusually quickly, being three to five times more toxic than that of any of the mainland species (2)(4)(6)(9).

The golden lancehead is also more arboreal than other species, able to climb trees in search of birds, and is active during the day, at the same time as its prey (2)(4). In addition to birds, some lizards and amphibians may be taken, and the juvenile golden lancehead feeds mainly on scorpions, amphibians, lizards and other snakes (4).

The golden lancehead is thought to mate between March and July, before giving birth to live young the following January to April. Litter size is smaller than in the mainland species, at around 2 to 10 young, compared to 18 to 30 in Bothropoides jararaca(4)(6)(10). The young measure around 23 centimetres in length at birth (2), and may be more nocturnal than the adults (4). The golden lancehead is unusual in that it appears to exist as three sexes: males, females, and ‘intersex’ females, which possess both female and reduced male genitalia (4)(6)(11).

Golden lancehead range

The golden lancehead is endemic to the island of Queimada Grande, off the coast of São Paulo, southeastern Brazil (1)(4)(5)(6)(8). This tiny island has a total area of only 43 hectares (0.43 square kilometres) (1)(4).

Golden lancehead status

Golden lancehead threats

The golden lancehead has one of the largest population densities of any snake (4). However, its overall population is relatively small, between 2,000 and 4,000 individuals (4)(12), and is restricted to a single, tiny island, where its habitat is under threat from deforestation and burning (1)(4)(11). Its population is believed to have decreased in recent decades, exacerbated by the removal of snakes from the island for the illegal wild animal trade (4)(11)(12)(13).

Although most of Queimada Grande is now protected, many areas that were deforested in the past are now covered with grass, and could take years to return to forest. The golden lancehead is particularly vulnerable to these threats because of its low reproductive rate and highly restricted range, which means that any environmental disaster to hit the island could eliminate the entire population (4).

Golden lancehead conservation

Bothropoides species are highly venomous and are considered to be particularly dangerous to humans, as a group being responsible for about 90 percent of all serious snakebites in South America (6). However, in recent years studies have shown the venom of the golden lancehead to have practical applications for humans, with many potential medical uses, making it even more important to protect this snake (4).

A number of studies and conservation efforts are underway to increase knowledge of the golden lancehead’s biology and ecology, and to monitor its population. More effective enforcement on the island is recommended to prevent illegal removal of snakes (4)(12)(13). Plans are also underway to develop a captive breeding population, as an ‘insurance policy’ against the loss of the species in the wild, and this may also aid further studies into the species’ biology and its venom, without the need to capture wild individuals (4)(13). Educational programmes among the local population may also help decrease illegal activities on Queimada Grande, so helping to secure a future for this unique snake (13).

Martins, M., Sawaya, R.J. and Marques, O.A.V. (2008) A first estimate of the population size of the Critically Endangered lancehead, Bothrops insularis. South American Journal of Herpetology, 3(2): 168-174.

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